A typical rotor seal assembly in a turbomachine is disposed between a stationary casing and a rotating shaft, where the rotating shaft penetrates an annular division wall that seats a sealing member at its inner-most diameter. A carrier ring is typically interposed between the division wall and the sealing member, thereby providing a connection device that allows for the replacement and/or upgrade of the seal without having to replace the whole division wall. Although many varying types of seals can be used, normally labyrinth, damper, and/or hole pattern seals are used in such applications. In operation, the face of the seal is disposed generally parallel to the shaft and configured to separate a high-pressure cavity from a low-pressure cavity, thereby minimizing the loss of pressurized fluids through the tight clearance defined between the shaft and the seal.
Elevated pressures, however, can deflect the division wall and cause a “coning” effect on the seal assembly. Coning occurs when the inner-most diameter of the seal assembly proximate the shaft is deflected by the pressures in the high-pressure region toward the low-pressure region, thereby diverging the seal face from its parallel disposition with the shaft. In this diverged disposition, the seal inlet creates a choking effect and the seal outlet acts like a diffuser, both of which phenomena can significantly alter seal characteristics and introduce rotor dynamic instability. Coning is enhanced by the connection joint between the carrier ring and the seal, which is typically a T-slot or similar rail fitting that can have a significant amount of play therebetween. As the pressure increases on one side of the seal assembly, the play between the carrier ring and the seal tends to augment the coning effect, thereby resulting in increased rotor dynamic instability.
What is needed, therefore, is a seal assembly that reduces or eliminates altogether the adverse effects of coning on a seal assembly.